炭化过程中的竹材收缩率

在温度为200～900℃的炭化过程中，通过测定6年生毛竹竹材的收缩率和竹炭得率，集中研究了竹材收缩率的各向异性及其与竹材主要组成之间的关系。结果表明：(1)在炭化过程中的相同炭化温度下，毛竹竹材在轴向、内部弦向、径向及外部弦向的收缩率依次增大。将竹材在200℃时处理3h，其轴向收缩率仍为零；(2)在整个炭化过程中，炭化温度在200～400℃范围内竹材收缩率的变化最大；(3)炭化温度低于400℃时，竹材中某一方向或部位的纤维素含量越高，其收缩率越大。炭化后期，竹炭的石墨化程度对竹炭收缩率可能有较大的影响；(4)加热温度低于300～350℃时，含水率越高的竹材，其收缩率越高。

A Study on Shrinkages During the Carbonization of Bamboo

Shrinkages have been investigated by means of measuring yields of solid products of carbonized bamboo and the variety of dimension in the carbonization process of bamboo,under the heat treatment temperature from 200℃ to 900℃.The paper focuses on the feature of shrinkages and the relationship between the shrinkages,moisture and polymer components in bamboo.The results show that,(1)By thermal conversion of bamboo,the rule of shrinkages in various directions show a similar way as that of the weight loss.From 200℃ to 400℃,shrinkages are most drastic.(2)Shrinkages of bamboo in various directions show an anisotropic feature.At a fixed carbonization temperature,according to a sequence of exterior tangential,radial,interior tangential,axial,the value of shrinkage increase continuously,which in axial direction below 200℃ is zero.(3)Below 400℃,cellulose,especially those in ordered regions,not only determines the orientation of shrinkages but also has a most significant influence on the degree of shrinkages in various directions.(4)Above 400℃,graphitization of bamboo charcoal possibly plays a more and more important role in shrinkages in its various directions.(5)Below the range from 300℃ to 350℃,raw bamboo or some internodes with the higher moisture perform the higher shrinkages.